Pylon of Sydney rail bridge riddled with 'concrete cancer'

Thousands of passengers travel over a railway bridge connecting Sydney to the Central Coast every day, despite a crucial supporting pylon being riddled with "concrete cancer".

With cracks up to two metres long, the pylon is so severely deteriorated it crumbles away like powder, but the NSW government has done nothing to replace it, despite knowing of the fault for more than two years.

Every day 11,000 passengers travel across the Hawkesbury River Rail Bridge to and from the Central Coast.

Sydney Trains received a report in 2013 revealing the pillar was in need of attention but they decided to wait.

An independent report commissioned by the NSW Transport Minister said the bridge remains safe for use in the short term but recommends repairs be carried out within six months.

"If we thought this bridge was unsafe, the railway would stop, we'd fix the bridge and we would continue on," Sydney Trains chief executive Howard Collins said.

"We've looked at all other rail bridge structures that Sydney Trains looks after and we have a thumbs up for all of those."